Molding material and method of producing the same



a Patented Jan. 14, 1941- UNITED STATES PATENT OFFICE MOLDING MATERIALAND METRO) OF PRODUCING THE SAME Herman J. Beboulet, Melrole, Mam,assimor to The Mood Corporation, Chiiiicothe, Ohio, a corporation ofOhio No Drawing.

Amputation July 11, 1930,

Serial No. 90,265

4 Claims.

is to provide a method adapted for the treatmentoi-spent digestionliquors resulting in the chemi cal direction oi fibrous materials toproduce pulp in the paper industry to produce therefrom a re- .coveredllgnln material which is moldahle in itseli, and which lends itscli toedective intermixture with other moldable andilller materials w toprovide molded products of Superior commercial characteristics.

another object is to produce such an orsanlc recovered material.

it is a iurther object to provide a process in W the recovery of suchnon-cellulosic material which process is coordinated with the usualrecovery system in the paper making plant in a highly economical manner.

llther objects and advantages will be apparent at irom the specificationand the appended claims. its is well known, it has been the practice iormany years to produce most pulp tor the man ulacture oi paper, and likeproducts from materials such as wood, straw and the like by subiectlngsuch fibrous material to so-callcd chemical digesticn,--the fibrousmaterial generally heing immersed in the chosen digestion liquid andcooked under proper conditions oi temperature, pressure, etc. Whilethere are sev- 35 eral well known forms oi cook, the best lmown termsare the so-called sulfite, sulfate or kralt and soda-the names beingindicative of the characteristics of the chemicals lorming the maindigestive portion of the cooking liquor. Genorally speaking the processis the same; but the resulting spent digestion liquor, in each of theseveral iorms oi cook, will contain chemical compounds which aredependent upon the character oi the digesting chemicals in the originalcookinc liquor. in all of these digestions the chemical present reactswith part oi the natural materials oi the wood to remove the so-calledlimo-ins, pentosans and other non-cellulosic material, along with someportions of the cellulosic material, which are most readily affected bythe chemicals, leaving the cellulose fibers ireed of the honding andadhering materials which bind them' together to give the rigid characterand term tothe wood or other material which is 55 being treated. It isthis spent digestionliquor,

trial which is precipitated out.

generally known as black liquor, which is treated in the practicing atthis invention.

As clearly explaining the invention in its preferred embodiment,reference is made hereinalter, unless otherwise specified, to that blackliquor which results in the so-called soda cook. in that cook the woodis immersed in a solution oi a caustic soda, the proportions oi whichare well hnovvn in conventional practice, and the material is subjectedto cooking therein until the non-cellulosic materials have heen removedto nlve the desired resulting release oi the cellulose I fillers andfiher bundles. This hlacl: liquor irom the soda process is stronglyalkaline, even though the cool: reactions have been completed. It has ibeen tunnel that it this alkaline soda liquor is subjected to acontrolled neutralizing effect, with an acid such as carbonic acid,obtained by passing (202 through the liquor, and the pH value controlledwithin proper range, certain organic materials which are non-cellulosicin character and which are believed to be derived from the material oilignln origin which is found in the hlack liquor will be separated outwhich have peculiar characteristics as to iusihility, suscepti- 5 hilltyto hydrolizing, moldability and admixture with other materials, eitherhller or thermostatting molding materials, to give desired and $11--perior molded products.

When C02 is bubbled through such hlack soda liquor to eilect theneutralizing action llgneous derivative materialisprecipltatecl out ofsolution, the character of the ligneous derivative compounds heingcontingent upon the pH value as established hy this acid. And thequantity of such llgneous derivative material which is precipitated out,and it is believed also its molecular construction, is believed directlydependent upon the pH value established, which in turn is dependent uponthe hydrogen ion concentration of the neutralizing acid used. Theselignin derivative material organic compounds are oi indeterminatemolecular construction, the original lignin itself being probably amlrrture oi compler: organic molecules, and the lignin derivativematerial which is separated out by the neutralizing action is likewise amixture oi complex molecules of character so far not definitelydetermined. However, the pH value which is dependent upon the particularacid used and its hydrogen ion concentration, will determine thecharacter of lignin derivative molecules precipitated out, generallyspeaking the higher the hydrogen ion content the higher the molecularweight of the lignin derivative mate-- a is believed,

therefore, that in the practicing of this process the molecularconstruction of the lignin derivative material can be controlled by theproper selection of acid, as to its hydrogen ion concentration, and theresulting pH value, on the acid side, will be substantially a constantfor any particular acid that might be used, within any normal range ofconcentrations that could be used formed, or at least in any controllingquantity,

and therefore the final characteristics of a lignin derivative materialmay be determined and controlled by the selection of the neutralizingacid to give a properly controlling pH value within the solution as thelignin derivative material is being precipitated therefrom.

Furthermore it has been found that as the acid neutralizing agent ischosen so as to produce lignin derivative material which constitutes apredetermined separated proportion with respect to the original materialavailable, that particular material will have characteristics as tomoldability, etc., which are contingent upon or proportional to therelative amount of material removed. Therefore, by so controlling the pHvalue and the precipitating effect that a given proportion ofligninderivative material is obtained from a predetermined amount ofblack liquor, the constituents and the characteristics of the resultingderivative material may be controlled according to predetermined desiredvalues.

Very satisfactory results in utilizing the above for the production ofsuch lignin derivative material from black liquor have been secured,using the digestion or black liquor from the soda pulp process.Preferably the process is carried out using a black liquor which hasbeen suitably concentrated to contain a greater proportion of solidsthan in its initially produced state, but not in such concentratedcondition as to interfere with proper separation of the lignin materialtherein. In operations on a plant scale, very satisfactory results havebeen secured using a black liquor in which the solids had been increasedto about 16% to 17%, the desired concentration of liquor beingconveniently secured by blending suitable quantities of the liquor fromdifferent stages of the evaporators. With such black liquor the desiredcontrolled results may be secured through the utilization of carbondioxide gas to effect the neutralizing action. This gas when bubbledthrough the black liquor, at room temperatures, will reduce thealkalinity to a narrow pH value range between pH 7.8 and pH 9, thisrange normally lying between pH 7.9 and pH 8.5. It is found that as thepH values decrease. it becomes more difficult to absorb additional CO2into the liquor. Also on a plant scale the stack gas available containsa diluted CO2 gas and for these reasons the pH value may suitably becarried down to about pH 8.3. In some cases the liquor has a tendency tofoam as the CO2 is passed therethrough. Such foaming may usually becontrolled by the action of a stirring member operating vigorously inthe layer of foam and in the topmost zone of the liquid. An antifoamingagent such as Turkey red oil or the like, may be added in smallquantity, a fraction of a percent, and will further tend to preventobjectionable foaming. With the alkalinity reduced to this pH value itis found that precipitation of lignin derivative material from the blackliquor, in proportion of approximately 25% of the original solids in theblack liquor, will result, and this lignin derivative material is ofsuch chemical, etc., characteristics, that it will function verysatisfactorily, in a superior manner and provide for obtaining productsnot heretofore known. The precipitated material is quite fine andremains in suspension. To facilitate subsequent filtration the suspendedno'n-cellulosic matter is subjected, either simultaneously orsubsequently, to a! coagulating action, preferably by heating thesuspension to a predetermined temperature range. While thenon-celluloslc matter can be separated from the liquor with diflicultyin the absence of heating as a coagulating step, a heating toatemperature range of the order of 50 C. to or C. is found to greatlyassist in the filtration and to shorten the time required. A heatingmaterially beyond the range specified is undesirable as it tends toeffect the formation of a gummy mass very difficult to filter and tohandle. It appears however that a higher coagulating temperature may beused when more effective agitation is secured. The liquor is heatedpreferably by means of a steam coil and is also preferably agitatedsimultaneously with the heating to assure uniformity of temperaturethroughout.

Prior to filtration, it is desirable to cool the liquor to substantiallyroom temperature, as it is found that the filtration of the liquor whilehot is diflicult and results in a product of undesirablecharacteristics. The liquor may be cooled by running a cooling fiuidthrough the coils and is preferably simultaneously agitated bymechanical means or by the introduction of air jets or the like.

Following the cooling the liquor is filtered on a suitable filter pressand the filtrate, containing the larger part of the digestion chemicals,is pumped back to the evaporators of the usual recovery system. Theprecipitate on the filter is then preferably washed with water to removesoluble compounds from the non-cellulosic matter, such compoundsincluding the remainder of the treating chemicals, such as sodiumcompounds in the case of the soda process, and the soluble organiccompounds such as alkali metal salts of organic acids. The wash watermay also be returned to the usual recovery system inasmuch as itcontains a certain quantity of the treating chemicals which it isdesirable to recover.

The precipitated matter at this stage of the processing is a thickcolloidal suspension, similar to a gel and in this form there is stillretained in occluded form a relatively material quantity of the blackliquor which it is difiicult to filter out by any ordinary filteringprocess. This liquor may contain caustic and also organo-metalliccompounds which are undesirable as deleteriously affecting the moldingand fusing characteristics of the lignin product.

Accordingly the precipitated matter is then treated with a strong acid,such as sulfuric acid, in an amount slightly in excess of that requiredfor neutralization. Being an electrolyte, the ac'd breaks up theagglomerated gel formation, facilitating filtering. And remaining tracesof caustic are neutralized and the objectionable organometalliccompounds are broken down. It is also found that such acid treatmentimproves the resistance of the material to hydrolysis and tends toproduce a material having a lower fusion point,

both of these characteristics being more particu- I greatly reduced.

The neutralized precipitate is then washed to remove acid, and anysoluble salts and the washed material may be then dried either at roomtemperature or more rapidly in a drier at a suitable temperature belowits fusion point, for example,

' ,at 150 0. and is then broken up or pulverized in any desired manner.

its a specific example oi the carrying out of the invention, thefollowing is given. The black liquor irom the soda process, specificgravity approximately 1.12 and pH value of 11 to 12, is

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pumped into a wooden treater tank, equipped with. I a spider type gas.inlet. The black liquor is treated with purified stack gas, from astack gas recovery system, for approximately 24 hours at which time ithad a pH value of 8. It is then pumped into a wooden coagulating tankequipped with heating and cooling coils and a. similar gas inlet. Theliquor is heated to 60 C. by means of the steam heating coil, and isthen cooled by running water through the cooling coil. The heatingoperation requires several hours while the cooling operation extendsover a somewhat longer period, the contents oi the tank loeingcontinuously agitated during the whole time. The liquor then pumped intoa. wooden reservoir tank e uipped with agitating means. l rom thereservoir tank the liquor is pumped at a pressure of ti lhs. per squareinch into the lllter press, which preieraloiy is a lead lined Sweetlandfilter. "lime iiltrate is pumped hack to the evaporator and carriedthrough the usual'recovery system in the paper mill plant.

iii'ash water is then pumped through the filter to wash out the solublecompounds, this wash water also lacing returned to the recovery system.Tests have shown that the wash water should be added in approximatelythe ratio or 3000 gallons to 2000 gallons oi black liquor of thecharacter above described, such method resulting in a total recovery atapproximately 08% of the caustic present in the black liquor. Thereafter500 gal-= ions oi water containing 20 pounds of sulfuric acid,representing a small excess of acid, is pumped through the filter andrecirculated for npproiuniately l0 minutes and then drained 01!. "lineprecipitated material is again washed with 0000 gallons of water towashout the acid and remaining soluble salts. If it is not desired torun the that or alkaline wash water through the recovery system, thewhole or a part thereof may he run into the second or acid wash waterand the neutralized wash water then run into the sewer. The washedmaterial is then removed irom the filter press, dried on a drum dryerand pulverized in a Raymond pulverizer. A material produced in thismanner is round to have a insion temperature oi the order of 180 C. to200 C. Furthermore the ligning product as so produced is oi suchcharacteristics that its melting or iusing temperature is subject tocontrol, in a manner to provide meltingtemperatures reduced below thevalue mentioned, if desired. Thus a lignin material can he producedhaving melting point characteristics within the range oi conventionalphenol iormaldehyde resins, such as to he directly mixalole and fusibletherewith. For example, llgnin produced in accordance with the presentmethod may" have controlled melting point characteristics imparted to itof approximately 90" to 100' C. Reference is made tocopendingapplication Serial No. 29,168 filed June 29, 1935, for disclosure of themethod 0! thus obtaining controlled melting, point characteristics.

It is found that the material so produced is very low in ash and in.organic-metallic compounds, the ash content of several runs fallingwithin a range of'.03% to .10% ash. The above results were obtained byusing distilled water for washing, and somewhat larger ash contents areobtained when a relatively hard water is used, the ash in the lattercase running up to approximately 1% ash. For most uses, however, it isfound that the higher ash content does not produce objectionable resultswhere the ash results from materials present in hard water and consequently the use of hard water is a commercially practicable method ofcarrying out the invention.

The product of this invention, besides being relatively pure andsubstantially ash free, is nomogeneous, is water insoluble inhighdegree, is

hold resistant, is resistant to such solvents as hencol, carbontetrachloride, and ether, and is round to have very desirablecharacteristics for use as a hinder material in molding, iuelbriquetting, and the like. It also has the desirable property ior somepurposes of high solubility in diethylene oxide, phenols, pyrogallol,henzaldehyde aldol, diethylene glycol nionocthylether, and is alsolargely aoluhle in acetone, alcohol, and mixtures thereof. The processis extremely simple maires use of inexpensive materials, and is socoordinated with the usual recovery process in the paper making plantthat it provides tor the carrying out of the present invention inconiunction with the usual recovery system ior the recovery of causticas inthe said process.

When this material is mixed with a filler such .as wood hour, asbestos,oariion lblack, or kieselguhr, and hot pressed in a. mold, it serves asa highly eflective binder and the resulting molding material has verydesirable properties. It is readily fusible, hasthcrmoplasticproperties, and can he repeatedly cooled and reheated without obtaininga permanent set. When this material is used in excess of 30% lay weightoi the molding composition, the product is iound to have good strengthand low water absorption characteristics. Furthermore, it is resistantto sulfuric acid, solvents such as naphtha and loenzol, and lubricatingoil.

The material oi this invention can be satisfactorily molded over a widerange or temperatures and pressures but the molding is preferablycarried out under conditions oi. the order of those of standardpractice. Thus for instance, a mixture of hetween 30 to 00% of thehinder of this invention, and 70% to 20% iiller can be molded i withvery satisfactory results at temperatures of the order of 175 C. andpressures of the order of 1100 lbs. per square inch, with a molding timeof two minutes. the product being thermoplastic, it is placed in themold and subjected to heat and pressure, the mold then being allowed tocool while the pressure is maintained.

The binder material of this invention can be used as a substitute forall or a part of known thermoplastic hinders in molding compositions, anexample of such known thermoplastic binder lacing shellac. As an exampleof the practicing of this invention in which. the present binder constitutes the sole binder material of the molding composition, a moldingcomposition comprising 40% by weight of a binder material derived fromthe non-cellulosic portion of woody fibrous material and 60 by weight ofwood flour was molded at a temperature of 177 C. and a pressure of 1100lbs. per square inch. It was found to have the desired low waterabsorption, solvent resisting, etc.,- properties above described. Inappearance the surface of the molded article was a bright shiny black,changing to a brown finish only after extended exposure to water.

As an example showing the use of the binder in conjunction with mineralfiller materials, the molding composition comprised 28% by weight of abinder derived from the non-cellulosic portion of woody fibrousmaterial, by weight of barytes, 35% of rotton stone, and 2% by weight ofgum copal, forming a molding compound having thermoplasticcharacteristics, and producing a very hard surfaced material.

As another example of the carrying out of the invention, a mixture ofsuitable proportions of binder and filler was placed ina cold mold andthe mold brought up to temperature under pressure. Somewhat improvedresults as regards uniformity and low water absorption were obtained bythis process, the binder and the filler being in contact for a longerperiod of time permitting more thorough intermixture ,and impregnationof the filler by the binder.

The binder is also usable in conjunction with or in substitution forother binder materials to provide for obtaining a desired effect whenthe molding material is subjected to heat and pressure.

Thus when used alone as the binder, or when used with other bindershaving thermoplastic properties, the molded product is of thermoplasticcharacter. However, the binder material of this invention may also beused in conjunction with a binder having thermosetting characteristics,such as phenol-formaldehyde resin, to provide a thermosetting moldedproduct. When the thermosetting binder is present in amounts of 50% ormore by weight of the total binder, the remainder comprising the binderof this invention, such thermosetting binder exercises a dominant effectupon the product and the molded product has desirable thermosettingproperties. And by reason of a substantial quantity of the material ofthis invention, the product is produced less expensively. Thus forinstance a thermosetting material may be provided comprising 50% to 60%of a suitable filler, and 50% to 40% binder of which 50% or morecomprises a thermosetting binder material such as phenol-formaldehyderesin, and up to 50% comprises the binder derived from the noncellulosicportion of woody fibrous material. The thermosetting material of theabove composition is found to be practically unaffected by boiling waterand has a resistance to solvents comparable with that of the ordinarymolded materials in which the binder consists entirely ofphenol-formaldehyde resins and the like.

As in the case of the thermoplastic compound, the thermosetting compoundcan be molded over a wide range of temperatures and pressures butpreferably the molding conditions are made approximately those nowstandard practice in the art. For instance, with a mixture comprising byweight 50% wood flour, 35% phenol-formaldehyde resin, and 15% of binderderived from the non-cellulosic portion of woody fibrous material 30% ofthe binder being such non-cellulosic portion of woody fibrous material),the mixture has been satisfactorily molded at a temperature of C. and apressure of 1900 lbs. per square inch,

the molding time being 1% minutes. The materials are mixed in anydesiredmanner, such as by grinding or milling, and a cold molded pill is made.The pill is then introduced into the mold, which has been heated to thedesired temperature, and the pressure is applied, the pressure beingmaintained for a predetermined time and then released without cooling.The molded product has good strength, low water absorption, so that itis resistant even to boiling water, is resistant to acids and ordinarysolvents, and is thermosetting.

The present invention therefore provides a binder material available inlarge quantities and at low cost, which can be used very satisfactorilywith a filler either alone or in conjunction with other known bindermaterials in molding compounds, either to produce a thermoplasticcompound, or when used in conjunction with a binder having thermosettingproperties, to produce such thermosetting molding compound. Furthermoreno material departure from standard molding practice or apparatus isrequired.

While the processes and products herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise processes and products, and that changesmay be made therein without departing from the scope of the inventionwhich is defined in the appended claims.

What is claimed is:

1. The method in the treatment of black liquor from the paper pulpingindustry, and the like, to recover therefrom a lignin derivativematerial which comprises subjecting such liquor substantially in itsinitial condition to a neutralizing action by passing a carbon dioxidecontaining gas therethrough, carrying such neutralizing forward to acontrolled pH value of approximately pH 7.8 to pH 9 to precipitate fromthe black liquor a separated fraction of said lignin materialconstituting a fraction up to approximately 25% of the total solids insuch liquor, separating and washing the precipitated lignin, and addinga strong acid to said precipitated lignin material while approximatelyat room temperature in an amount substantially that required forneutralization.

2. The method in the treatment of black liquor from the paper pulpingindustry, and the like, to recover therefrom a lignin derivativematerial which comprises subjecting such liquor substantially in itsinitial condition to a neutralizing action by passing a carbon dioxidecontaining gas therethrough, carrying such neutralizing forward to acontrolled pH value of approximately pH 7.8 to pH 9 to precipitate fromthe black liquor a separated fraction of said lignin materialconstituting a fraction up to approximately,25% of the total solids insuch liquor, separating and washing the precipitated lignin, and addinga strong acid to said precipitated lignin material in an amountsubstantially that required for neutralization and for breaking down oforgano-metallic compounds.

3. The method in the treatment of black liquor from the paper pulpingindustry, and the like, to recover therefrom a lignin derivativematerial which comprises subjecting such liquor substantially in itsinitial condition to a neutralizing action by passing a carbon dioxidecontaining gas therethrough, carrying such neutralizing forward to acontrolled pH value of approximately pH 7.8 to pH 9 to precipitate fromthe black liquor a separated fraction of said lignin materialconstituting a fraction up to approximately 25% of the total solids insuch liquor, heating said suspension to a temperature 01 approximately50 C. to 90 C. to cause coagulation and agglomeration of theprecipitated particles while avoiding formation of a gummy mass thereof,separating and washing the precipitated lignin material, and adding astrong acid to said precipitated lignin material in an amountsubstantially that required for neutralization and for breaking down oforganemetallic compounds.

4. The method in the treatment of black liquor from the paper pulpingindustry, and the like, to recover therefrom a lignin derivativematerial which comprises subjecting such liquor substantiallyin itsinitial condition to a neutralizing action by passing a carbon dioxidecontaining gas therethrough, carryng such neutralizing forward toacontrolled pH value or not in excess of approximately pH 8.5 and withina rangeto precipitate from the black liquor a separated traction of saidlignin material constituting a fraction up to approximately 25% of thetotal solids in such liquor, separating and washing the precipitatedlignin, and adding a strong acid to said precipitated lignin material inan amount substantially that required for neutralization and forbreaking down of organo-metallic compounds.

HERMAN a. REBOULET.

